This is kind of a return to an old thread. The main point here is that,
just as the man Christ Jesus is excepted from original sin (including original sin
as described in various places in Romans, with such
statements by St. Paul as "all have sinned and fallen short of the
glory of God" and "death passed to all men
because all have sinned") and just as that fact can be demonstrated from
specific Scriptural verses when those verses are correctly understood,
Mary is excepted from original sin and this fact can be demonstrated
from specific verses. One well-known verse that shows this is Luke 1:28, and
particularly the angel Gabriel's salutation to Mary: "Chaire,
Kecharitomene" (translated in the Douay-Rheims and other
Catholic versions as "Hail,
Full of Grace" or "gratia plena" in the Latin
Vulgate).

To a virgin espoused to a man whose name was Joseph, of the house of David: and the virgin's name was Mary.
And the angel being come in, said unto her: Hail, full of grace, the Lord is with thee: blessed art thou among women. Who having heard, was troubled at his saying and thought with herself what manner of salutation this should be. And the angel said to her: Fear not, Mary, for thou hast found grace with God.
(Luke 1:27-30 Douay-Rheims); [Latin Vulgate: ad virginem desponsatam viro cui nomen erat Ioseph de domo David et nomen virginis Maria
et ingressus angelus ad eam dixit have gratia plena Dominus tecum benedicta tu in mulieribus quae cum vidisset turbata est in sermone eius et cogitabat qualis esset ista salutatio et ait angelus ei ne timeas Maria invenisti enim gratiam apud Deum....]

Tangent time: In the old thread, one of our wizened protestant
fellow-travelers pointed out that the word Gabriel uses when saluting
Mary, "Kecharitomene"
is formed from the same root (charitoo)
as a word used in one of the great early Christian hymns (I wish that
the Catholic hymn writers would do a modern version, they actually
are pretty good at doing Scripturally-based hymns). The hymn appears in
the first chapter of Ephesians (ironically, the letter to the Ephesians was probably written by
Luke, as well, but this hymn probably was not, it probably pre-existed
the letter). There, the relevant stanza is

"for
the praise of the glory of his grace
that he granted us in the beloved" (Ephesians 1:6).

The variant of charitoo here is echaritosen.
While Kecharitomene is,
according to everything I've read, a perfect passive participle, echaritosen
is an indicative active aorist. Kecharitomene
means "having been" or "have already been"
graced, according to this
commentary on the Book of Zechariah -- talking about perfect passive participles in a different context and a
different verse [brackets indicate where I am inserting
"graced" for the word in the relevant text]:

"That which will accompany, and be a result of, Jewish
recognition, is a direct quotation from the Septuagint in Ps. 118:26,
'Blessed be he that comes in the name of the LORD.' This
verse also is better understood with a Greek analysis. The word
Blessed, 'eulogamenos' is a perfect passive
participle. It literally means 'having been blessed or praised.' The
'perfect' action of the participle is considered to have been
completed before the time of the speaker. How long before is not a
consideration but the Greek verbal idea is that the action has
already been completed. Time is still secondary but perfected
action must imply the past in relationship to the speaker. The person
using the word is confessing that the one referred to has already
been blessed [or graced]." (Zechariah and Jewish Renewal: From Gloom to Glory
by Fred P. Miller, chapter
31 on Zechariah 20)

Other examples of the perfect tense and what it means:

"There are seven tenses of the Greek verb. They are: the Aorist, Present,
Imperfect, Future, Pluperfect, and Future Perfect. Let us exemplify the Perfect and Present tenses. In the words of the Greek grammarian
J. Gresham Machen, 'The Greek perfect tense denotes the present state resultant upon a past
action' (New Testament Greek for Beginners, p. 187). The perfect is used in Matthew 4:4,7,10 ('it is written'). Literally translated,
'It has been written in the past and is still in force.' Hence, Jesus expresses the
continuing authority of God's written law by using the perfect tense."
("How
About the Greek Language?" from BibleQuestions.org)

"...Ephesians 2:8, 'For by grace are you saved through faith...' The word
'saved' is
translated from the Greek word sesosmenoi, which is a perfect passive
participle. It means that this salvation took place at some point in the
past and is continuing on in the present...." ("The
Lord is not Slack Concerning His Promise" from
CephasMinistry.com)

In other words, the perfect tense in Greek is a past
tense with a special meaning: it is used to refer to a past action which
has effects felt in the present. So, here's what some modern, English-speaking scholars tell us "Kecharitomene"
denotes, based purely on the definition of the word and its grammatical
usage:

" 'Highly favoured' (kecharitomene).
Perfect passive participle of charitoo and means endowed with grace
(charis),
enriched with grace as in Ephesians 1:6 . . . The Vulgate gratiae
plena [full of grace] "is right, if it means 'full of grace which thou hast
received'; wrong, if it means 'full of grace which thou hast to
bestow' "(A.T. Robertson, Word Pictures in the New
Testament, p. 14)

"It is permissible, on Greek grammatical
and linguistic grounds, to paraphrase kecharitomene as completely,
perfectly, enduringly endowed with grace."
(Blass and DeBrunner, Greek Grammar of the
New Testament).

However, Luke 1:28 uses a special conjugated form of "charitoo." It uses "kecharitomene," while Ephesians 1:6 uses "echaritosen," which is a different form of the verb "charitoo."
Echaritosen means "he graced" (or bestowed grace). Echaritosen signifies a momentary action, an action
brought to pass (Blass and DeBrunner, Greek Grammar of the New
Testament, p. 166). Whereas, Kecharitomene, the perfect passive
participle, shows a completeness with a permanent result.
Kecharitomene denotes continuance of a completed action (H. W.
Smyth, Greek Grammar [Harvard Univ Press, 1968],
p. 108-109, sec 1852:b; also Blass and DeBrunner, p. 175).

And our friend's citation of what the term denotes:

"...to bestow grace, to show favor to someone...the divine favor for
a special vocation...." (Fritz Rienecker/Cleon Rogers in
their Linguistic Key to the Greek New Testament)

Ironically, that final definition is essentially coextensive with the
Catholic understanding of the why of Mary's sinlessness --

Supreme Reason for the Privilege: The Divine Maternity

"And indeed it was wholly fitting that so wonderful a mother should be
ever resplendent with the glory of most sublime holiness and so
completely free from all taint of original sin that she would triumph
utterly over the ancient serpent. To her did the Father will to give his
only-begotten Son -- the Son whom, equal to the Father and begotten by
him, the Father loves from his heart -- and to give this Son in such a
way that he would be the one and the same common Son of God the Father
and of the Blessed Virgin Mary. It was she whom the Son himself chose to
make his Mother and it was from her that the Holy Spirit willed and
brought it about that he should be conceived and born from whom he
himself proceeds."
(Pope Pius IX, Ineffabilis Deus)

However, I still haven't really gotten to my argument: whatever the denotation of "chaire, Kecharitomene,"
its connotation, what it actually meant to ancient
Greek-speakers,
is why it is communicating precisely that Mary was immaculately
conceived.

The Greek Fathers

Here are a number of ancient experts and what they say it means; each of them is
a Greek-speaker from a culture basically identical to that of St. Luke;
there are a couple repeats from the previous thread, but from them I give new
material, too; the passages are expositions by the authors of the meaning
of Luke 1:28, generally centered on chaire, Kecharitomene:

Gregory Thaumaturgus (205-270 AD):

O purest one
O purest virgin
where the Holy Spirit is, there are all things readily ordered.
Where
divine grace is present
the soil that, all untilled, bears bounteous fruit
in the life of the flesh, was in possession of the incorruptible
citizenship,
and walked as such in all manner of virtues, and lived a
life more excellent than man's common standard
thou hast put on the vesture of purity
has selected thee as the holy one and the wholly fair;
and through thy holy, and chaste, and pure, and undefiled womb
since of all the race of man thou art by birth the holy one,
and the
more honourable, and the purer, and the more pious than any other:
and
thou hast a mind whiter than the snow, and a body made purer than any
gold

Akathist hymn (5th or 6th century AD):

Hail, O you, through whom Joy will
shine forth!
Hail, O you, through whom the curse will disappear!
Hail, O Restoration of the Fallen Adam!
Hail, O Redemption of the Tears of Eve!
Hail, O Peak above the reach of human thought!
Hail, O Depth even beyond the sight of angels!
Hail, O you who have become a Kingly Throne!
Hail, O you who carry Him Who Carries All!
Hail, O Star who manifest the Sun!
Hail, O Womb of the Divine Incarnation!
Hail, O you through whom creation is renewed!
Hail, O you through whom the Creator becomes a Babe!
Hail, O Bride and Maiden ever-pure!

"In the place of Eve, an instrument of death, is chosen a Virgin, most pleasing to God and full of His grace, as an instrument of life. A Virgin included in woman's sex, but without a share in woman's fault.
A Virgin innocent; immaculate; free from all guilt; spotless; undefiled; holy in spirit and body; a lily among
thorns." (Theodotus, Hom 6 in S. Deiparam, No 11; PG 77:1427A)
or another translation: "Innocent virgin, spotless, without defect, untouched, unstained, holy in body and in soul, like a lily flower sprung among
thorns, unschooled in the wickedness of Eve, unclouded by womanly vanity...Even before the Nativity, she was consecrated to the Creator...Holy apprentice, guest in the Temple, disciple of the law, anointed by the Holy Spirit, clothed with divine grace as with a cloak, divinely wise in your mind; united to God in your heart...Praiseworthy in your speech, even more praiseworthy in your action...God in the eyes of men, better in the sight of God." (Theodotus, Hom 6:11; Gambero, page 268)

"What did the divine messenger do then? Perceiving the Virgin's interior dispositions and perspicacity in her outward appearance and admiring her just prudence, he began to weave her a kind of floral crown with two peaks: one of joy and one of blessing; then he addressed her in a thrilling speech of praise, lifting up his hand and crying out:
'Hail, O full of grace, the Lord is with you, you are blessed' (Lk
1:28), O most beautiful and most noble among women. The Lord is with you, O all-holy one, glorious and good. The Lord is with you, O worthy of praise, O incomparable, O more than glorious, all splendor, worthy of God, worthy of all
blessedness....Through you, Eve's odious condition is ended; through you, abjection has been destroyed; through you, error is dissolved; through you, sorrow is abolished; through you, condemnation has been erased. Through you, Eve has been redeemed.
He who is born of the holy [Virgin] is holy, holy and Lord of all the saints, holy and Giver of holiness. Wondrous is he who generated the Woman of wonder; Ineffable is he who precedes the Woman beyond words; Son of the Most High is he who springs from this highest creature, he who appears, not by man's willing it, but by the power of the Holy Spirit; he who is born is not a mere man, but God, the incarnate Word."
(Theodotus, On the Mother of God and on the Nativity; Patrologia orientalis 19:330-1;
Gambero, page 271)

According to Fr. Luigi Gambero, author of Mary and the Fathers of the
Church, "This kind of apostrophe addressed
to the Virgin occurs frequently in Greek homilies of the fifth century
onward; it constitutes a literary form called chairetismoi, from the
Greek word chaire, which translates as 'hail' or 'rejoice' (cf.
Luke 1:28)."

"[T]he Lord said to his Mother,
'Let your heart rejoice and be glad, for every favor and every gift
has been given to you from my Father in heaven and from me and from the
Holy Spirit. Every soul that calls upon your name shall not be ashamed,
but shall find mercy and comfort and support and confidence, both in the
world that now is and in that which is to come, in the presence of my
Father in the heavens'" (The Falling Asleep of Mary).